The invention pertains to a ventilation device of a vehicle such as an agricultural vehicle, which has an engine and a cooling device, with which the engine and/or additional parts to be cooled are in a heat conducting relationship, while the ventilation device comprises a fan with a fan drive, by means of which ambient air is fed to the cooling device, and a control system connected to the fan drive, which is provided to regulate the air feed rate of the fan.
Known from U.S. Pat. No. 4,828,088 A is a ventilation device for use in trucks or automobiles, in which a control system with sensors for the temperature of the vehicle engine and the respective speed, is provided. By means of a viscous coupling, the rotary speed of a fan is adjusted in such a way that the engine is adequately cooled but the lowest possible energy requirement and a minimal noise generation are achieved.
Disclosed in U.S. Pat. No. 5,584,371 A is a similar ventilation device. Here the speed of a fan is regulated in relation to the temperature of the coolant and the rotary speed of the engine. In the normal operating range, the rotary speed of the fan is proportional to the rotary speed of the engine.
In the field of self-propelled harvesters, a tendency to ever-increasing engine power can be observed. Since the speed of these machines is often very low during the harvesting process and the rotary speed of the engine is comparatively high, suitable measures must be taken to cover the cooling output requirements. In addition, cooling output must be provided for a number of other systems. Consequently, the capacity for heat dissipation is, as a rule, made available by the air feeding capacity of large fans.
Inasmuch as known control devices for rotary speed of fan have not proven to be expedient in actual practice, e.g., due to high shifting frequencies and uncontrolled acceleration occurrences, fixed fan drives are generally in use at the present time. However, as a rule, the output requirement of fan increases with the square of drive motor speed and, depending upon the fan type, reaches as high as 10% of the total engine output at high engine rotary speeds. In many cases, e.g., in roadway drivingxe2x80x94which can constitute as much as 30% of the machine operationxe2x80x94only a part of this fan output is really needed, so that the energy consumption of the harvester is unnecessarily high.
The problem underlying the invention is to make available an improved ventilation device.
The solution according to the invention makes allowance for two essential values as initial parameters: the requirement of the cooling device for ambient air and the feeding rate of the fan. In the light of these parameters, the feeding rate of the fan is adjusted in such a way that it is operated in a manner that maximizes energy-savings yet covers the cooling requirement. Thus, in keeping with the invention, allowance is made by the control system for both the requirement of the cooling device for ambient air and the operating energy of the fan. In particular, the control system makes it possible to execute the acceleration operations of the fan in a controlled manner.
In this way, an energy-saving ventilation device which lowers the fuel consumption and the operating costs of the vehicle is obtained. Furthermore, the disturbing noises of the fan, e.g., when the vehicle is operated on the roadway, are reduced to a minimum level. By virtue of the control system, it is possible to install a given fan on vehicles of various cooling requirements, since the feeding rate of the fan commensurately controls the respective requirement. Thereby the number of different parts which must be made ready for the production of various vehicles is reduced.
The control system specifically allows for the load moment of the fan dependent upon the quantitative feed, i.e., the relationship between the driving torque (or the driving power) and the respectively fed quantity of air. In addition, the moment of inertia of the fan is allowed for, which represents the energy for accelerating the fan to the rotary speed corresponding to the respective quantitative feed. Thus the control system is charged with information as to how much energy is required to accelerate the fan to a certain rotary speed (representing a certain quantitative feed). In this manner it is possible to make allowance for the xe2x80x9ccostsxe2x80x9d of a change, especially an increase, of the feeding rate of the fan, when determining the feeding rate. Unnecessary rotary speed changes, which also place undue mechanical stress upon both the fan and the fan drive, are then reduced to a minimum. Allowance can also be made for the moments of loss of the fan; they are usually due to friction or slipping. With the energy-saving selection of the feeding rate, it is also possible to ensure that the engine does not unnecessarily heat up due to the driving torque build-up required for the fan.
It is additionally proposed that the control system calculate the requirement of the cooling device for a predetermined period of time and adjust the fan drive to a constant feeding rate for this period. A reasonable period of time is, e.g., one minute.
In order to determine the given requirement of the cooling device for ambient air, the control system can be connected to one or more sensors. In this manner, it is possible to monitor the temperature of the ambient air, the temperature of a coolant of the cooling device, the temperature of a hydraulic fluid and the rotary speed of the engine. Furthermore, the rotary speed or the feeding rate of the fan can be monitored, so that it can be compared with the reference value calculated by the control system and adjusted as necessary.
The control system can be equipped with a flat logic. Such logics are known and produce association functions for one or more input variables for the control system and determine, by way of a regulator, output values, with which the feeding rate of the fan is adjusted.
The opportunity of designing the feeding rate to be continuous, i.e., infinitely variable, presents itself, although a stepped adjustment would also be plausible, which is realizable, e.g., with a transmission with several gear settings. For the continuous adjustment of the feeding rate, hydraulic transmissions or so-called CVT transmissions (continuous variable transmission) present themselves. The latter are known from the automobile industry and have a drive belt running around two belt pulleys. One of the belt pulleys is conical and the drive belt is so arranged as to be laterally adjustable thereon. A hydraulic drive consists of a pump with an adjustable feeding output and a hydraulic motor. The use of a viscous coupling is also plausible, as described in the US patent documents cited above.